Graft-versus-host disease (GVHD) may occur whenever immunologically competent allogenic lymphocytes are transfused to an immunocompromised host. This risk has been minimized by irradiating blood products before transfusion to prevent donor lymphocytes from dividing, engrafting, and establishing an immune response against the recipient following transfusion. In institutions with access to a blood product irradiator, the blood products are irradiated immediately prior to transfusion. In many institutions, however, the lack of easy access to an irradiator necessitates that an inventory be maintained of blood products that have been irradiated elsewhere. The purpose of this project is to determine the effect of 3000 Rad irradiation on in vitro function and in vivo survival of red cells stored for the maximum permissible time (42 days) in the preservative solution AS-1 (Adsol). Eight normal volunteers have been recruited for the study. Each subject has donated two units of whole blood (450 ml each) into AS-1 blood preservative solution. One unit was collected and stored normally as packed red cells at 4 degrees C for 42 days. The other unit was irradiated on a rotating turntable with 3000 Rad within 4 hours of collection using a cesium-137 blood irradiator and then stored for 42 days. Six of the subjects donated a third unit that was irradiated with 3000 Rad on a stationary platform. There was a significant decrease in posttransfusion red cell survival and ATP, and a significant increase in supernatant potassium in the irradiated units. This suggests that 3000 rad significantly damages red blood cells.